Question 31
Domain 3: Floor Construction and Supporting FramingWhat is the minimum required bearing for floor joists on concrete or masonry per the IRC?
Correct answer: C
Explanation
IRC Section R502.6 requires floor joists to have a minimum bearing of "1 1/2 inches" on wood or metal and "3 inches" on masonry or concrete. That is why the minimum required bearing for floor joists on concrete or masonry is 3 inches.
Why each option is right or wrong
A. 1-1/2 inches
B. 2 inches
C. 3 inches
IRC Section R502.6 sets the bearing requirements for floor joists and distinguishes between support materials: joists need at least 1 1/2 inches of bearing on wood or metal, but 3 inches when bearing on concrete or masonry. Because the question asks specifically about concrete or masonry support, the controlling minimum is 3 inches.
D. 4 inches